Carlson, who once worked with Kristol at the Weekly Standard, said Kristol’s remark was “libel, but also really stupid.” It went downhill from there for Kristol.

“Last night at the top of the show, we addressed the removal of Civil War monuments from public places around the country. We made the point that the sudden outrage isn’t entirely about slavery, horrifying as slavery is. It’s also part of a larger effort on the left to discredit the Founders of this country and the beliefs they enshrined in law,” Carlson explained.

“Once you believe that any figure in history who once owned slaves is illegitimate and should be erased, it’s hard to take our founding documents very seriously. How can you accept a Bill of Rights when it was written by slave owners? You can’t. Which is why so many on the left don’t — and ignore the First and Second Amendments, among many others. That was the point we were trying to make. You may disagree but it didn’t seem crazy or mean spirited.”

Responding to that segment on Tuesday night, Kristol wrote in a tweet that went viral among liberal journalists: “‘They started by rationalizing Trump, they ended by rationalizing slavery.” Kristol also accused Carlson of being anti-Semitic, offering no evidence whatsoever to support his claim.

“That is libel. But it’s also really stupid,” Carlson said Wednesday night. “And yet Bill Kristol isn’t stupid. I know that because I worked for Bill Kristol for more than five years in the 1990s. I knew him well. He was a genuinely smart guy. He was a good boss, too. He was humane and fair-minded. He was the kind of person I never would imagined would write something that nasty and dishonest about an enemy, much less an old friend. What happened?”

“Kristol refused to explain himself today. Part of the explanation has to be the moment we’re living in where hysteria has supplanted rational debate. No longer to explain your beliefs but to highlight what a morally upstanding person you are, a virtuous guy you are, using by contrast of your opponent who is by definition, evil. It’s childish, obviously. But to many people, it’s tempting. Even 64-year-old men with Harvard degrees fall for it, apparently,” Carlson continued.

“Part of the problem is the medium. Twenty years ago, when he had something to say, he had a magazine to say it in. He talked through ideas with his friends before spending hours writing a piece that expressed it precisely. There was thinking involved in the process. Now he just goes on Twitter and stays on Twitter all day, every day, dashing off thoughts and impressions, scoring tiny little points against strangers in cyberspace, keeping obsessive track of his likes and retweets,” Tucker said.

“At an age when he could be playing with his grandchildren, he’s glued to social media like a slot machine junkie in Reno. after a while, that distorts you. When you disagree with someone it doesn’t occur to you to hash it out. You tweet it hoping for retweets. Depressing as hell. Kristol isn’t the only one who does this. Washington is littered with formerly impressive people who shout and preen on social media. I hate to see it with him. I liked Bill Kristol once and thought he liked me. What a shame.”